Electric Power Steering Motor Control Using Six-Sector Vector Transformation
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Solution Overview
Problem
Conventional electric power steering apparatuses require significant computational resources and increase costs due to the use of trigonometric functions and square roots in dq-coordinate transformations, making them inefficient for microcomputer processing and design changes.
Innovation Solution
A control method and unit that transform two-phase command values into three-phase command values by separating the vector region into six sectors, using a simplified calculation method that specifies the sector based on signs and amplitudes, reducing the need for trigonometric functions and improving processing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional dq-coordinate transformation methods using trigonometric functions and square roots are employed, then transformation accuracy is maintained, but computational complexity and processing load increase significantly
Solution Approach 1:
The transformation method divides the coordinate space into six distinct sectors based on the angle range. Each sector has its own simplified transformation equations that avoid trigonometric functions. By segmenting the problem space, the patent achieves accurate transformation in each sector while maintaining computational simplicity, thus resolving the contradiction between transformation accuracy and computational complexity.
Solution Approach 2:
The patent changes the transformation parameters by using sector-specific linear equations instead of universal trigonometric formulas. Within each sector, the transformation uses simple algebraic operations with predetermined coefficients rather than computationally intensive sine and cosine calculations. This parameter change maintains accuracy within each sector while dramatically reducing computational complexity.
2Productivity
If simplified transformation methods are used to reduce computational load, then processing efficiency improves, but transformation accuracy may deteriorate
Solution Approach 1:
By dividing the transformation space into six sectors, the patent enables the use of simplified linear equations in each sector while maintaining overall transformation accuracy. The segmentation ensures that the simplified method remains accurate within each sector's angular range, thus improving processing efficiency without sacrificing transformation precision.
Solution Approach 2:
The patent applies different transformation equations tailored to each sector's specific characteristics. Each sector has its own optimized transformation formula that is locally accurate for that angular range. This local quality approach ensures high transformation accuracy within each sector while maintaining overall system efficiency, resolving the contradiction between simplified processing and accurate transformation.
3Reliability
If conventional transformation algorithms are implemented in microcomputers, then complete transformation functionality is achieved, but processing time and computational resources increase
Solution Approach 1:
The six-sector segmentation enables the microcomputer to use simple algebraic operations instead of complex trigonometric calculations. Each sector's transformation can be completed with basic arithmetic operations, significantly reducing processing time while maintaining complete transformation functionality across all angular ranges.
Solution Approach 2:
The patent pre-calculates and stores transformation coefficients for each sector in advance. During real-time operation, the microcomputer only needs to determine the current sector and apply the corresponding pre-prepared equations, eliminating the need for runtime trigonometric function evaluations. This preliminary action reduces processing time while preserving complete transformation capability.
Data Source
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AI summary
[Problem] An object of the present invention is to provide a control method and a control unit of an electric power steering apparatus that simplifies a calculation of a transformation from a two-phase command value to a three-phase command value performed in the case of driving and controlling a motor mounted on the electric power steering apparatus, reduces a load of the calculation, and enables installation to a microcomputer. [Means for solving the problem] A control method comprises a transformation step of transforming a two-phase command value calculated from the current command value into a three-phase command value; the transformation step separates a region for a vector consisting of the two-phase command value into six sectors, and transforms the two-phase command value into the three-phase command value in accordance with a calculation method that is predefined in each sector and is simplified; and the electric power steering apparatus drives the motor in accordance with the three-phase command value.